When hair is blonded—more particularly when hair is blonded at home by consumers themselves—the problem is that natural tints become completely covered, making multi-tone hair blonding difficult to realize.
In order to lend the hair a natural appearance, partially decolorizing both non-dyed and already dyed hair by the targeted application of oxidants is known from the prior art. The hair sections (“strands”) to which the oxidant is applied typically bleach in portions, the result being a multi-tone hair color. Dyeing individual hair sections (“strands”) with a different color is also known from the prior art. The oxidant, possibly comprising dye, is applied to the hair by means of a brush or similar tool, wherein the hair that is to remain untreated is protected against contact with the oxidant, possibly comprising dye, by means of solid, flat separating means, more particularly with soils from solid materials, such as aluminum, paper or Styrofoam and similar materials, or by means of a so-called “highlighting cap”. Such a highlighting cap is disclosed in WO 2007/087978, for instance.
With the prior art highlighting method, the foils or the highlighting cap accumulate at the end of the method as solid waste, which must be discarded. This causes an environmental load. Handling the foils is difficult in part; for example, access to as yet untreated hair is obstructed by foils already in place. Moreover, foils made of paper, plastic and Styrofoam can adhere to the treated hair poorly and slip out.
Certain foil types and applications can involve overheating, because the possibility of dissipating the reaction heat of the exothermic oxidation process by evaporating volatile formula constituents, such as water for example, is severely restricted by the steam-impermeable foils.
Most foil types are not transparent. To be able to control the color development—especially towards the end of the specified application time—the foil must be at least partially handled, which can disrupt the color development process and, moreover, hinders the work sequence.
Blonding agents, particularly those that are supposed to achieve a strong lightening effect (“high lift”), typically contain a large quantity of ammonium hydroxide as the alkalizing agent. During the application time, usually at least from about 30 minutes to about 60 minutes, ammonia leaks out. In addition to the odor nuisance and mucous membrane irritation, this also reduces the effect of the agent during the lightening process. Moreover, blonding agents tend, particularly if not covered by highlighting foils and applied over large areas instead, to dry out during this relatively long application time, which also reduces the lightening effect. To compensate for the reduction in the lightening effect caused by drying out, a higher hydrogen peroxide concentration than is actually needed is typically selected for the oxidant. This can, in turn, lead to more severe structural damage to the keratin fibers and/or to a more severe irritation of the scalp than would actually be necessary.
Patent Applications EP2574331A2 and WO2014164213A1 disclose dyeing methods that permit multi-tone dyeing or blonding in one dyeing step, wherein a thickening agent, more particularly an anionic or cationic associative polymer (EP2574331A2) having a thickening effect is added to a hair blonding or bleaching agent in higher concentrations before application to selected hair sections or strands. The dye thickens on the hair strands to form a highly-viscous paste, thereby achieving a separating effect to adjacent hair sections or strands. The color exchange between adjacent strands, which were treated with various blonding or bleaching agents, is thus minimized. Over the total dye application time of approx. 30 to 60 minutes, the dye diffusion between adjacent strands, which are in physical contact with one another, cannot however be completely avoided. The corresponding commercial product for professional salon use is therefore marketed with the instruction that the color difference between adjacent strands should not be more than about 3 color tones. Otherwise, the color result would be impaired by a visible color exchange.
The present disclosure addressed the problem of preparing a method that permits multi-tone blonding in one process. The present disclosure also addressed the problem of preparing the most resource-efficient multi-tone blonding or lightening method possible, which involves no solid foil waste and uses, wherever possible, only materials from sustainable, non-fossil-based raw materials. In addressing this problem, it was particularly important for the foil substitutes to have a high separating force, just like the flat foils. In other words, permitting the cleanest possible separation of the various colored or bleached fiber sections or fiber strands, without any blonding agent exchange between the adjacent strands, which would result in broader stands being decolorized than actually intended. The present disclosure also addressed the problem of preparing a multi-tone blonding or lightening method that permits a simplified visual check of the decoloration development.